Many down the hole (DTH) devices such as but not limited to motors, pumps and DTH hammers operate by channelling a working fluid such as air, nitrogen, water, oil or mud through a drill pipe to operate the device.
The working fluid is pressurised and delivered at a pressure and rate dependent on many factors including the capacity of the driving compressor/pumping system; pressure losses through the drill pipe and DTH device itself; the mechanical limitations of the DTH device and environmental fluid pressure.
Consider for example a common DTH reverse circulation (RC) hammer (herein after “RC hammer”). The RC hammer comprises: an outer case which is coupled to a down hole end of the drill string; an inner tube; a porting sleeve; a hammer or piston which is able to slide along the inner tube and within the outer casing; and a drill bit. Fluid pumped down the drill string enters a porting arrangement between the outer case and the inner tube and reciprocates the piston to cyclically impact the drill bit. This transfers kinetic energy into the material at the toe (bottom) of the hole to fracture and displace the material. This material is delivered by residual fluid energy through the inner tube to the surface. This material can be analysed to provide information on the mineralogy and geology of the substrata.
Current RC hammers are deliberately designed to be inefficient with reduced mechanical energy output. This is to enhance mechanically reliable of the RC hammer when driven by compressors which provide excessive fluid pressure and flow rate to the work chamber when drilling short holes. It is known that inline pressure loses increase with hole depth (i.e. drill string length). So for short holes there is minimal inline pressure lose through the drill string. But the fluid pressure and flow rate provided by the compressors/boosters is designed for a deeper target depth. Consequently to protect the hammer as it progresses to the target depth current design practise is to reduce internal port efficiency and thus mechanical output of the hammer to protect bearing and striking surfaces of a piston and the bit from material and lubrication failures when used with excessive airpower. As a result of these in-built inefficiencies, when it is desired to drill deeper, then larger compressors are required especially to produce sufficient pressure differential at the piston (work chamber), to enable driving of the hammer drill bit and to compensate for additional in line losses as the length of the drill pipe increases. This leads to increased operational costs due to the power requirements of the compressors to do useful work at the bottom of deep holes, needing to overcome increasing additional line losses, and the designed and built-in flow restrictions.
The above described background art is not an admission that the art forms part of the common general knowledge of a person of ordinary skill in the art. Further, the above references are not intended to limit the application of the disclosed down the hole hammer and the systems and components thereof. Specifically, the above references are not intended to limit application of the systems and components to use only with or in a DTH hammer or DTH RC hammer.